1. Field of the Invention
The present invention is generally directed toward receiver-transmitter systems referred to as Family Radio Service (FRS) units, although the invention is not limited to this embodiment. The Family Radio Service is one of the Citizens Band Radio Services. It is intended for the use of family, friends, and associates to communicate among themselves within a neighborhood or while on group outings. There are fourteen discreet FRS channels available for use on a xe2x80x9ctake turnsxe2x80x9d basis. The FRS unit channel frequencies are:
Other selected technical specifications are:
(a) Frequency modulation (although phase modulation is allowed);
(b) Frequency tolerance of each FRS unit must be maintained within 0.00025%;
(c) The authorized bandwidth for an FRS unit is 12.5 kHz; and
(d) Effective radiated power (ERP) shall not, under any condition of modulation, exceed 0.500 W.
The operating rules for the FRS are found at 47 C.F.R. 95.191-95.194. For additional technical information, see 47 C.F.R. 95.601-95.669.
2. Related Art
Modern day communication systems employ components such as transmitters and receivers to transmit information from a source to a destination. To accomplish this transmission, information is imparted on a carrier signal and the carrier signal is then transmitted. Typically, the carrier signal is at a frequency higher than the baseband frequency of the information signal. Typical ways that the information is imparted on the carrier signal are called modulation.
The present invention is directed to a communications system with an image-reject down-converter. The invention has a number of aspects, including a ultra-low power down-converter, an image-reject down-converter, and a high-efficiency transmitter. In an embodiment, the present invention is used in a family radio system. It is to be understood, however, that the invention is not limited to this particular embodiment. Other implementations in communications-related environments are within the scope and spirit of the invention.
The present invention has a number of advantages, including power reduction, tuning reduction, parts reduction, price reduction, size reduction, performance increase, greater efficiency, and increased integration possibilities.